Crystallisation and precipitation

Technology
Technology details
Name:	Crystallisation and precipitation
Category:	Pre-processing (Separation technologies), Post-processing (Separation technologies)
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Salt crystals at Great Salt Lake, Utah, USA

Crystallisation is the formation of crystals from a solution. In a crystal, the atoms or molecules are highly organised into a solid repetitive structure. "A solution is a mixture of two or more species that form a homogenous single phase. Solutions are normally thought of in terms of liquids, however, solutions may include solids suspension. Typically, the term solution has come to mean a liquid solution consisting a solvent, which is a liquid, and a solute, which is a solid, at the conditions of interest. The solution to be ready for crystallization must be supersaturated."

A simple example for crystallisation is the evaporation of the solvent. For example, the salinity of the Great Salt Lake in Utah, USA, is so high that through the evaporation of water salt crystals cover its shores. Some other ways in which crystals form are precipitating from a solution, freezing, or more rarely deposition directly from a gas. Attributes of the resulting crystal depend largely on factors such as temperature, air pressure, and in the case of liquid crystals, time of fluid evaporation.

Feedstock

NaCl (table salt) crystal consisting of sodium and chlorine atoms

Origin and composition

The feedstock for crystallisation is a solution with crystallisable ingredients, e.g. minerals or organic molecules. The majority of minerals and organic molecules crystallise easily, and the resulting crystals are generally of good quality, i.e. without visible defects. However, larger biochemical particles, like proteins, are often difficult to crystallise. The ease with which molecules will crystallise strongly depends on the intensity of either atomic forces (in the case of mineral substances), intermolecular forces (organic and biochemical substances) or intramolecular forces (biochemical substances).

Process and technologies

Crystallisation occurs in three major steps. The first is nucleation, the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The second step is known as crystal growth, which is the increase in the size of particles and leads to a crystal state. An important feature of this step is that loose particles form layers at the crystal's surface and lodge themselves into open inconsistencies such as pores, cracks, etc.

Crystallisation is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs. In chemical engineering, crystallisation occurs in a crystalliser. Crystallisation is therefore related to precipitation, although the result is not amorphous or disordered, but a crystal.

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Company name	Country	Technology category	Technology name	TRL	Capacity [kg/h]	Processable volume [L]	Feedstock: Food waste	Feedstock: Garden & park waste
Company 1	[Country HQ location]	[Technology category (if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]		●	●
Company 2	[Country HQ location]	[(if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]		●	●

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Crystallisation and precipitation provider

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Technology name:		Technology category:	Pre-processing (Separation technologies), Post-processing (Separation technologies)
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